Glass has been used as a material for lenses (in particular, vehicle-mounted camera lenses), because the glass has heat resistance, transparency, and dimensional stability at excellent levels. However, the glass, even being a low-melting glass, has a high melting temperature of about 400° C. or higher and has poor workability. In addition, the glass causes high production cost, because heat upon glass shaping impairs the mold (shaping die), and this impedes repeated use of the mold. Accordingly, the use of resinous materials as an alternative to the glass has been investigated actively.
A known resinous material for lenses employs thermoplastic resins such as cycloolefin polymers and polycarbonates (Patent Literature (PTL) 1). These resins, however, have poor heat resistance and are impracticably used in vehicle-mounted camera lenses and other applications that require heat resistance.
As a possible solution to solve the heat resistance issue, there is proposed a technique of using an epoxide structurally including an isocyanurate ring as a principal skeleton (PTL 2). The epoxide, however, has poor curability and is hardly applied to the use as a material for wafer-level lenses, where the material has to be cured rapidly by heating for about 2 to about 3 minutes. In addition, the cured product of the epoxide is susceptible to yellowing and hardly maintains its transparency when exposed to a high-temperature environment for a long term.